Van der Zalm Metal Industry connects banks and frameworks

When we think of steel structures, we think of Brakel. There, Van der Zalm Metaalindustrie BV works every day on the most diverse steel structures. With its own engineering department, Van der Zalm builds many steel structures in the Netherlands. Designing, assembling, welding and assembling voluminous structures for our civil engineering and industrial customers is a daily job. The delivery program includes mooring facilities, bridges and bridge parts, offshore facilities, tubular pile structures, shipbuilding and machine building. We are the guests of Kees Van der Zalm, managing director, and Simon Knaap, project leader/R&D manager, to review a few special bridges.

Roosendaal rolling bridge

A nice bridge to start with is the Roosendaal rolling bridge, commissioned by Aannemingsbedrijf Damsteegt & Aannemingsbedrijf Vissers Ploegmakers, to a design by Maters and de Koning. The canary yellow colossus is a pedestrian bridge connecting the Stadsoevers neighborhood to the station area. The bridge crosses De Vliet and runs in a Z-shape to the other side. Kees: "This bridge has a semi-permanent character. It actually has a static presence throughout the year, which is why seats have also been created on the bridge. Every month the bridge is opened, but especially when Sinterklaas comes over De Vliet with his boat. Then the 29-meter-long bridge rolls about 18 meters up the quay, over rails. You can imagine that we had to add an enormous amount of counterweight to keep the bridge from tilting." 

Waterland road bridge (Circle Bridge)

A special project, says Simon. "We are building a bicycle and pedestrian bridge over the Waterlandseweg (N305) and the Hoge Vaart in Almere, near landscape artwork the Groene Kathedraal and business park Stichtsekant." The new connection is an asset to the bicycle path network and routes for recreational walkers. In total, the bridge spans some 240 meters with a maximum width of 7.5 meters. Built on 4 fixed piers (center) and 10 hinged piers (distributed along its length). Kees: "The bridge consists of 6 sections, of which 4 sections were transported by water and 2 sections by road. The heaviest section weighs about 100 tons." A nice detail is the spiral staircase and elevator placed halfway up the bridge. Noteworthy is the design of the bridge. "In the pleated and curved shapes there was a lot of similarity to shipbuilding which we also have the necessary experience with," Simon explains. "The challenge was in the length and in the connections. The bridge was cut up, but calculated as one continuous beam, which only gets its strength when the joints are connected. This was the most critical point in the design. The connecting joints were all fully post-machined on our own milling machine after welding. Responsible for the design are Aannemingsbedrijf Reimert and wUrck Architectuur en Landschap. The lead structural engineer in this project is Arup."

About the choice of materials, Kees says: "In terms of shape and material, the bridge fits beautifully into the landscape. Corten steel and wood were used. Van der Zalm did all the UO calculations for this bridge in collaboration with PT STructurals. Another special feature is that no fewer than 500 M36 10.9 bolts were used, which had to be fully preloaded, with about 50 tons of tensile force per bolt. Because the bridge is flexible, you can't get the joints flat. The space between the flanges was injected with Diamond, ultra strong filler material." In conclusion, Simon concludes, "The bridge was a truly wonderful challenge for us to build, thanks to our client, Aannemingsbedrijf Reimert. Van der Zalm can fully express its specialty in this type of job."